Mn-Bi powders with High Coercivity and Magnetization at Room Temperature

摘要

Mn_(55)Bi_(45) + x at.% Mn (x=0, 7 and 11) magnetic powders were prepared by low energy ball milling technique. The x-ray diffraction pattern showed that the samples mainly contain over 90% of the low temperature Mn-Bi phase (LTP) for x= 0 and 3 with a very small amount of Bi phase. Microstructural analysis showed that the amount of sub-micron particles increases with milling time. The TEM studies of the 8 hours milled Mn_(55)Bi_(45)+ 7 at. % Mn samples showed that the average grain size is in the range of 20-30 nm. The milling time dependent magnetic properties were studied for all the compositions. An intrinsic coercivity (H_(ci)) of 12.2 kOe, remanent magnetization (4πM_r) of 7.1 kG, and energy product (BH)_(max) of 11 MGOe have been obtained for the 8 hours milled Mn_(55)Bi_(45) + 7 at.% Mn sample. These Mn-Bi powders have potential use as precursor for rare earth free permanent magnets.